The invention relates to failure mode and effects analyses (FMEA) and particularly to FMEA of rotary power generation units.
Power generation units, and particularly units generating electrical power for utility companies, are often required to operate continuously for extended periods at high levels of reliability. Meeting these requirements is difficult because power generation units are prone to wear and require regular maintenance.
Power generation units typically have large rotating components, operate under extreme conditions, and are subjected to large mechanical and electrical loads. These units wear and will suffer failure if the units are not properly maintained. To avoid failure, the power units are scheduled to be taken off-line for periodic repair and maintenance.
A schedule of the repair and maintenance of power generation units typically involves setting a period during with a unit is continuously operated between successive off-line repair and maintenance events. The duration of this period usually requires a balance of the requirement for reliable operation of the unit and the need for continuous and extended operation. When undergoing repair and maintenance, a power generation unit is off-line and is not generating power for a power grid. If the period between successive off-line repair and maintenance events is too long, the power unit may fail during operation which results in an unplanned outage of power generation. Shortening the period reduces the overall period during which the unit is generating power and reduces the total amount of power generated by the unit over an extended period including one or more off-line sessions.
A calculated risk of failure is conventionally used to determine the period between planned off-line maintenance and repair events for an industrial power generation unit. This risk of failure is used to balance the requirement for reliability of the power unit with the need for generated power.
The calculated risk of failure may be characterized as a risk of the power generation unit suffering an unplanned outage. A power unit suffers an unplanned outage when the unit is taken off-line at a time other than a scheduled off-line period. The unplanned outage is typically due to a failure of a power generation unit operating in the field such as in a power generation plant.
Unplanned outage risk is traditionally determined based on historical data of actual field failures of power generation units. Actual field failures are useful for estimating the risk of failure, but do not accurately account for all risks involved in operating the power generation unit. Some risks are not reflected in the historical failures of units.
To model these other risks a “lurking model” has conventionally been used. For example, the risk to previously unseen failure modes may be estimated using lurking model. The lurking model approach is crude and is based on a hypothetical analysis of unforeseen and unseen modes of failures. A lurking model takes into account the risk associated with those unknown failure mode(s) of the system or system components which may precipitate in future if the system or component is allowed to operate beyond the current known operating experience. The risk is typically estimated by a lurking model using a Weibayes model, which is a type of Weibull model in which the shape parameter, also know as “beta”, is assumed. A typical value of beta is relatively high and may be in a range of 3 to 4. The hypothetical analysis used in the lurking model may not anticipate actual unforeseen failure modes of a power generation unit.
There is a long felt and unsolved need for enhanced systems and methods to accurately assess the risk of an unplanned outage failure, and to anticipate the modes of failure that can occur in a power generation unit.